title: PB1-mediated virulence attenuation of H5N1 influenza virus in mice is associated with PB2.
abstract: H5N1 avian influenza viruses demonstrate different phenotypes, such as pathogenicity after one or serial passages in mammalian hosts or cells. To establish the molecular basis of these phenotypes, we cloned isolates from the lungs of mice infected with human A/Vietnam/1194/2004 (H5N1) influenza virus. Large-plaque isolates were less pathogenic to mice than small-plaque isolates. Genome sequencing revealed that the small-plaque and large-plaque isolates differed in several amino acids. In order to assess their effects on pathogenicity in mice, two amino acid changes common to attenuated isolates, one in PB2 (I63T) and the other in PB1 (T677M), were inserted into a wild-type recombinant virus construct. The PB2 (I63T) or PB1 (T677M) mutations alone did not alter the phenotype of H5N1 virus, whereas recombinant virus with both mutations was less pathogenic than the wild-type recombinant virus. Furthermore, the PB1 (T677M) mutation showed a lower replication efficiency, although it had higher polymerase activity. The recombinant virus with the PB2 (63T) mutation replicated as well as the wild-type recombinant virus. These results suggest that the C terminus of PB1 of H5N1 influenza virus mediates virulence attenuation of H5N1 influenza virus in mice, associating with the N terminus of PB2. However, the role of the N terminus of PB2 in virulence attenuation in mice remains unclear.
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Guohui
authors.initials: G
authors.lastname: Chang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Wei
authors.initials: W
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Yinhui
authors.initials: Y
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Kang
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Pathogens and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, PR China.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Zhu
mesh_terms: D000818:Animals; D002460:Cell Line; D005260:Female; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D007251:Influenza, Human / Q000401:mortality / Q000821:virology*; D008168:Lung / Q000821:virology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D014779:Virus Replication
chemical_list: C502893:PB2 protein, influenza virus; D014764:Viral Proteins; C077346:influenza virus polymerase basic protein 1